1. Technical Field
The present invention relates to a semiconductor technology, and particularly to a method of forming an isolation structure.
2. Description of Related Art
Implementing electric circuits involves connecting isolated devices through specific paths. When fabricating silicon integrated circuits it must therefore be possible to isolate devices into the substrate from one another. These devices can subsequently be interconnected to create the specific circuit configurations desired. From this perspective, isolation technology is one of the critical aspects of fabricating integrated circuits.
A variety of techniques have been developed to isolate devices in integrated circuits. One reason is that different types of devices (e.g., high voltage devices and low voltage devices) have different isolation requirements. respectively. However, conventional technologies have the following drawbacks:
(1) The isolation field implant of a field oxide has a junction depth shallower than the well of a trench oxide, and has a light ion concentration, thereby having an unsatisfied isolating capability.
(2) A trench oxide has a well isolating devices better than the above field oxide well does, it is still not deep enough.
For this or other reasons, there is a need for a method to fabricate an isolation structure which satisfies those different requirements.